AP Chemistry — Unit 6 Progress Check:
MCQ
1.
HCl(aq) + NH3(aq) -> NH4+(aq) + Cl-(aq)
The chemical reaction between HCl(aq) and NH3(aq) is represented above. A
student combines equimolar amounts of HCl(aq) and NH₃(aq), both solutions
initially at 24°C, in a coffee-cup calorimeter. The student observes that the
mixture reaches a temperature of 28°C. Based on the experimental results, which
of the following can be concluded about the reaction?
A)
It is an endothermic process, because energy is released by the reaction and is
gained by the reaction mixture.
B)
It is an endothermic process, because energy is absorbed by the reaction and is
lost from the reaction mixture.
C)
It is an exothermic process, because energy is released by the reaction and is
gained by the reaction mixture.
D)
It is an exothermic process, because energy is absorbed by the reaction and is
lost from the reaction mixture. - ANS - C. It is an exothermic process, because
energy is released by the reaction and is gained by the reaction mixture.
\2.
When pellets of NaOH(s) are added to a flask of water, it is observed that the
temperature of the water increases as the pellets dissolve. Which of the following
claims about the observed dissolution of NaOH(s) in water is most accurate?
A)
It is an endothermic process because heat energy is absorbed by the water as the
NaOH(s) dissolves in it.
, B)
It is an endothermic process because heat energy is released by the water as the
NaOH(s) dissolves in it.
C)
It is an exothermic process because heat energy is absorbed by the water as the
NaOH(s) dissolves in it.
D)
It is an exothermic process because heat energy is released by the water as the
NaOH(s) dissolves in i - ANS - C. It is an exothermic process because heat energy
is absorbed by the water as the NaOH(s) dissolves in it.
\3.
An advertisement for a commercial hand warmer claims that the hand warmer
works because a chemical reaction in the hand warmer draws out the body's own
natural heat, causing a warming effect. Which of the following states the accuracy
of the claim in the advertisement and best provides a correct scientific
justification of the claim?
A)
The advertisement's claim is inaccurate because heat flowing from the hands to
the warmer would only happen if the chemical reaction was endothermic, which
would cause the hands to feel colder.
B)
The advertisement's claim is inaccurate because heat flowing from the hands to
the warmer would only happen if the chemical reaction was exothermic, which
would cause the hands to feel colder.
C)
The advertisement's claim is accurate because heat flowing from the hands to the
warmer would only happen if the chemical reaction was endothermic, which
would cause the hands to feel warmer. - ANS - A. The advertisement's claim is
inaccurate because heat flowing from the hands to the warmer would only
happen if the chemical reaction was endothermic, which would cause the hands
to feel colder.
\4.
A student carefully drops a 9.0g solid Zn pellet initially at 50.0°C into an insulated
cup containing 30.0g of water at 27.8°C. The student predicts that the temperature
MCQ
1.
HCl(aq) + NH3(aq) -> NH4+(aq) + Cl-(aq)
The chemical reaction between HCl(aq) and NH3(aq) is represented above. A
student combines equimolar amounts of HCl(aq) and NH₃(aq), both solutions
initially at 24°C, in a coffee-cup calorimeter. The student observes that the
mixture reaches a temperature of 28°C. Based on the experimental results, which
of the following can be concluded about the reaction?
A)
It is an endothermic process, because energy is released by the reaction and is
gained by the reaction mixture.
B)
It is an endothermic process, because energy is absorbed by the reaction and is
lost from the reaction mixture.
C)
It is an exothermic process, because energy is released by the reaction and is
gained by the reaction mixture.
D)
It is an exothermic process, because energy is absorbed by the reaction and is
lost from the reaction mixture. - ANS - C. It is an exothermic process, because
energy is released by the reaction and is gained by the reaction mixture.
\2.
When pellets of NaOH(s) are added to a flask of water, it is observed that the
temperature of the water increases as the pellets dissolve. Which of the following
claims about the observed dissolution of NaOH(s) in water is most accurate?
A)
It is an endothermic process because heat energy is absorbed by the water as the
NaOH(s) dissolves in it.
, B)
It is an endothermic process because heat energy is released by the water as the
NaOH(s) dissolves in it.
C)
It is an exothermic process because heat energy is absorbed by the water as the
NaOH(s) dissolves in it.
D)
It is an exothermic process because heat energy is released by the water as the
NaOH(s) dissolves in i - ANS - C. It is an exothermic process because heat energy
is absorbed by the water as the NaOH(s) dissolves in it.
\3.
An advertisement for a commercial hand warmer claims that the hand warmer
works because a chemical reaction in the hand warmer draws out the body's own
natural heat, causing a warming effect. Which of the following states the accuracy
of the claim in the advertisement and best provides a correct scientific
justification of the claim?
A)
The advertisement's claim is inaccurate because heat flowing from the hands to
the warmer would only happen if the chemical reaction was endothermic, which
would cause the hands to feel colder.
B)
The advertisement's claim is inaccurate because heat flowing from the hands to
the warmer would only happen if the chemical reaction was exothermic, which
would cause the hands to feel colder.
C)
The advertisement's claim is accurate because heat flowing from the hands to the
warmer would only happen if the chemical reaction was endothermic, which
would cause the hands to feel warmer. - ANS - A. The advertisement's claim is
inaccurate because heat flowing from the hands to the warmer would only
happen if the chemical reaction was endothermic, which would cause the hands
to feel colder.
\4.
A student carefully drops a 9.0g solid Zn pellet initially at 50.0°C into an insulated
cup containing 30.0g of water at 27.8°C. The student predicts that the temperature
